This invention relates to epoxy resin compositions. In one aspect, the invention relates to improving the properties, including flexibility and chemical stability, of epoxy coating formulations. In a specific aspect, it relates to methods of preparing epoxy resins having improved friability and processing characteristics for powder coating formulations.
Epoxy resins have achieved wide acceptance as coating materials for surfaces requiring a high degree of corrosion resistance. Epoxy resins for coating applications are available in both solid and liquid form, and a variety of methods are available to apply the resins to a surface to be coated. One common method is electrostatic deposition, in which a solid epoxy resin-based composition is applied to the surface as a finely-divided powder. For such an application method, it is desirable to have a solid epoxy resin which has good friability. "Good friability," in terms of epoxy powder coating compounding, includes a rapid rate of grinding and a narrow size distribution of the particles. Solid epoxy resins differ significantly in their grinding characteristics. Some resins which have excellent powder coating properties are difficult to grind into small particles. Taking the time to grind the particles adds expense to the process, while not insuring proper grinding compromises the quality of the coating. If the grinding properties of these solid epoxy resins could be improved, the results would be higher production rates during powder manufacture, better handling and application characteristics during powder deposition, and enhanced properties of the coating.
It is therefore an object of the present invention to provide a solid epoxy resin having improved grinding characteristics and enhanced powder coating properties. It is a further object to provide an economical means for producing a solid epoxy resin having a broad molecular weight distribution.